Seatbelt systems are used in numerous motor vehicles for the purposes of restraining occupants during maneuvering and impact conditions. Seatbelt systems are found in wide-spread applications, including the typical three-point variety found in passenger car motor vehicles, off-road vehicles, and other vehicles. In some instances, two-point-type belt systems are used, for example, they are frequently found in aviation use for aircraft crew and passengers.
The restraint effect provided by a seatbelt system maintains an occupant in a desired position in a seat and further serves to absorb energy during an impact event and in other conditions involving high acceleration loads. When a seatbelt system is loaded by the restraining effect on an occupant, significant forces are present. These forces appear both as tension forces on the seatbelt system as well as forces acting on the seat occupant. Such forces can exceed preferred magnitudes and it is therefore known to incorporate load limiting features into seatbelt systems. Examples of load limiting belt systems are found in passenger car seatbelt retractors which incorporate torsion bars and other features for energy absorption and to limit belt loads.
Aircraft applications place significant demands on the belt restraint systems due to weight and packaging space limitations, particularly when applied for passengers. Such belt systems are typically a two-point variety without a retractor device. Instead, a cinch-type buckle or latch plate is provided for adjusting the seatbelt to the occupant. As mentioned previously, load limitation and energy absorption features are desirable for many applications of belt restraints. In aviation use, energy absorbing features can reduce injury to occupants during hard landings. Any such devices provided for aviation use must be lightweight and compact to be commercially viable.